OBSERVATIONS OF INFRARED-LUMINOUS STARBURST GALAXIES

ABSTRACT

From the recent ASCA observations, X-ray spectra of ultraluminous infrared galaxies (ULIRGs) are usually composed of two components; a hard non-thermal coponent which represents a dust-enshrouded AGN, plus a soft thermal component. If the latter is an emission from collisional ionization plasma, it resresents a nuclear starburst activity, and the enoumous far-infrared emission of ULIRGs is concluded to be powered by nuclear starbursts. On the other hand, if it is mainly comes from photoionized plasma, the AGN activity may be much larger than thought so far. We propose to observe two nearby infrared-luminous starburst galaxies, to study the origin of the soft thermal component of ULIRGs, which will let us reveal the mystery of the power source of ULIRGs.